192.168.0.23
shows this: Unable to connect
Firefox can't establish a connection to the server at 192.168.0.23.
The site could be temporarily unavailable or too busy. Try again in a few
moments.
If you are unable to load any pages, check your computer's network
connection.
If your computer or network is protected by a firewall or proxy, make sure
that Firefox is permitted to access the Web.
var/www/ contains index.html, which contains
<html><body><h1>It works!</h1>
<p>This is the default web page for this server.</p>
<p>The web server software is running but no content has been added, yet.</p>
</body></html>

192.168.0.23
shows this: Unable to connect
Firefox can't establish a connection to the server at 192.168.0.23.
The site could be temporarily unavailable or too busy. Try again in a few
moments.
If you are unable to load any pages, check your computer's network
connection.
If your computer or network is protected by a firewall or proxy, make sure
that Firefox is permitted to access the Web.
var/www/ contains index.html, which contains
<html><body><h1>It works!</h1>
<p>This is the default web page for this server.</p>
<p>The web server software is running but no content has been added, yet.</p>
</body></html>

Click to expand...

It work! - is the standard apache welkome wile in /var/www/
It means, that you do not have any virtual hosts, or you didn't restarted your apache after adding it. If you did add a virtual hosts, please, restart your apache.

192.168.0.23
shows this: Unable to connect
Firefox can't establish a connection to the server at 192.168.0.23.
The site could be temporarily unavailable or too busy. Try again in a few
moments.
If you are unable to load any pages, check your computer's network
connection.
If your computer or network is protected by a firewall or proxy, make sure
that Firefox is permitted to access the Web.
var/www/ contains index.html, which contains
<html><body><h1>It works!</h1>
<p>This is the default web page for this server.</p>
<p>The web server software is running but no content has been added, yet.</p>
</body></html>

Click to expand...

So far that all looks good. If you are still having problems, please do the following as root, and paste the results here...